13 Nov
2007
13 Nov
'07
7:23 p.m.
Wow, a lot to go over here... Rich, if you have any problems with
your drive I might be able to help you after this exercise! : )
If that's a plain 7805, it'll only sypply 1A. And I could well believe an
S100 board of logic (including a 1771) _and _ a floppy drive could take
more than that. You might be having little power glitches caused by the
spindle motor, or when you step the head, that will really mess things up.
I would use a seprarate supply for the drive.
As regards grounds, it's ovbiously essential that the 0V line of the
drive and controller (and the rest of the S100 system) are all linked
together. But I've never hand any problems with not bonding the drive
chassis to ground, I suspect that unless you live in an eelctrically
noisy environment, you won't either.
Data is comming from the disk, however it's
not readable. Possible
reasons:
NOISE, ground the drive, insure it has good power that the
system case and it's grounds are common. Also common
error is long drive cables (stay short for now) and cables
(and drives) that get near CRTs.
I'm hooking the 3.5" drive power cable directly to the output of the
7805 on the tarbell, which is getting its power from an 8v switching
power supply. The power is nice and steady at 4.95v. The only thing
I haven't done is made sure the case is grounded. Some drives had
jumpers for that, but mine doesn't. So it could be either way. HD media is
incompatable in every way with older drives and lower
data rates.
My drive is a new from sony. I've made formatted and written to HD
disks with the HD hole covered. This same drive reading the same
disks does not always read. I don't know if its the tarbell's fault or not.
I've read that HD (1.44MB 3.5") disks with
tape over the HD hole
aren't exactly a DD disk. Something about the track width being
Coirrect. The coercivity of the HD media is a little higher. Not as bad
as the difference between 5.25" DD and HD disks, but it can still 'bite'
you sometimes.
narrower because of the smaller head in an HD drive?
BUT, the DD
(720k 3.5") disks were formatted to 40 tracks 18 sectors, 128 bytes a
sector using an HD drive. So the DD disks wouldn't have a wide track
width to begin with. Are there really physical media differences
When used ona PC, both 3.5" formats (720K and 1.44M) have 80 cylinders, 2
heads. The track spacing is the same (135 tpi). If you're only using 40
cylinders, my guess is that you're using the outer 40 cylinders of the
80-cylinder format, still at 135 tpi. This shouldn't be a problem.
-tony